The present application claims priority to Japanese Application No. P10-353341 filed Dec. 11, 1998 and Japanese Application No. P11-070792 filed Mar. 16, 1999, which applications are incorporated herein by reference to the extent permitted by law.
1. Technical Field
The present invention relates to an etching method and a method of manufacturing a magnetic head, and more specifically, to a method of manufacturing a magnetic head in which a magnetic gap is formed between non-magnetic materials provided on opposed surfaces of a pair of yoke cores which are formed to be opposed to each other on a substrate.
2. Background Art
In recent years, video tape recorders, audio tape recorders, computer data storage systems, and the like are known as magnetic recording/reproducing apparatuses which use a magnetic tape as a recording medium. As for the magnetic recording medium, there is a demand for increasing the recording density to enhance its capacity and to attain a high data transfer rate.
However, if the magnetic recording medium is improved to have a high recording density in a magnetic recording system, the magnetized information from the magnetic recording medium is so weakened that reproduced signals are difficult to detect for a conventional inductive type magnetic head using electromagnetic induction.
Hence, in bard discs or the like, a magnetic resistance effect type magnetic bead (which will be hereinafter referred to as an MR head) using a magnetic resistance effect element (which will be hereinafter referred to an MR element) made of a soft magnetic film such as NiFe alloy or the like has been used for reproduction of signals.
However, in case where the MR head is set in a helical scan tape system in which the magnetic head is mounted on a rotation drum and recording/reproducing is carried out while rotating the magnetic head, the MR element must be slid on a magnetic tape at a high speed, leading to a problem that the MR element is worn out. Once the MR element is worn out, serious problems are caused, e.g., the output and the bias amount changes, the operation stability is lowered, the resistance value changes, or so.
Therefore, a proposal has been made for a MR head of a yoke type in which an MR element is provided in the head and magnetic flux from a magnetic recording medium is guided to the MR element by a yoke core to reproduce signals. In this yoke type MR head, a pair of yoke cores made of a soft magnetic film are formed so as to be opposed to each other with a non-magnetic film inserted therebetween, on a substrate. The portions of the magnetic film provided at the opposed regions construct a magnetic gap.
In case where the magnetic gap is formed substantially in parallel with the surface of the substrate where a film is formed in the yoke type MR head as described above, the efficiency is degraded if the track width is narrowed as the recording density is increased to be high. Therefore, it is necessary that the magnetic gap is formed to be substantially vertical to the surface of the substrate where the film is formed.
FIGS. 58 to 66 show a first conventional method of forming a gap film. Note that FIGS. 58 to 64 and 66 are views showing the forming method of the magnetic gap film in form of cross-sectional views cut along the line Y1-Y2 in FIG. 65.
At first, as shown in FIG. 58, a Cr film 31 and a SiO2 film 32 are formed in this order on a substrate 30. Next, as shown in FIG. 59, a resist 33 is applied onto the SiO2 film 32 and is patterned into a predetermined shape. Specifically, a mask pattern is formed in which the resist 33 remains only one of parts of the substrate 30 divided along the portions where the magnetic gap is formed. Further, as shown in FIG. 60, etching is carried out with the mask pattern used as a mask, and the portions of the SiO2 film 32 which is exposed from the mask is removed.
Next, as shown in FIG. 61, a gap film 34 is formed entirely on the substrate 30 and the resist 33, with the resist 33 remaining. Next, as shown in FIG. 62, the resist 33 is peeled together with the gap film 34 formed on the resist. Further, as shown in FIG. 63, the remaining SiO2 film 32 is removed by reactive etching. At this time, the gap film 34 formed on the substrate is removed except for the portion thereof which forms finally a magnetic gap.
Further, as shown in FIG. 64, a magnetic film 35 which forms part of a yoke core is formed on the entire surface, and the surface is polished, thereby forming the gap film 34 to be substantially vertical to the film forming surface of the substrate 30. Further, yoke cores are patterned as indicated by a broken line in FIG. 65.
Also, FIGS. 67 to 76 show a second conventional method of forming a gap film.
At first, as shown in FIG. 67, a first magnetic film 41 is formed on the entire surface on a substrate 40. Next, as shown in FIGS. 68 and 69, a resist 42 is applied onto the first magnetic film 41 and is patterned into a predetermined shape. Specifically, the mask pattern should be such that the resist 42 remains on the portion which forms one of a pair of yoke cores. Further, as shown in FIG. 70, etching is carried out with the mask pattern used as a mask, to remove the first magnetic film 41 exposed from the mask. At last, the resist 42 is removed so that one yoke core is formed as shown in FIGS. 71 and 72.
Next, as shown in FIG. 73, a gap film 44 is formed on the entire surface, and further, a second magnetic film 45 is formed on the gap film 44. Further, the surface of the second magnetic film 45 is polished so that a pair of yoke cores are formed as shown in FIGS. 75 and 76 and part of the gap film 44 is formed to be substantially vertical to the film forming surface of the substrate 40. Further, as indicated by broken lines in FIG. 75, patterning forms the yoke cores.
In the conventional methods as described above, since yoke cores are formed one after another, the manufacturing steps are complicated. Also, in the second forming method, a difference in thickness appears between the yoke cores and causes a drawback that the off-track characteristic is deteriorated.
The present invention has been proposed in view of the actual situation of conventional techniques as described above, and has an object of providing an etching method and a method of manufacturing a magnetic head which are capable of forming a magnetic gap substantially vertical to the film forming surface of a substrate by a simple method with high accuracy.
According to the present invention, there is provided a method for manufacturing a magnetic head comprising a substrate and a pair of yoke cores formed on the substrate, provided so as to oppose each other, with a non-magnetic material provided between the pair of yoke cores thereby to form a magnetic gap, the method comprising: a non-magnetic film forming step of forming a non magnetic film made of the non-magnetic material on the substrate; a high selectivity film forming step of forming a high selectivity film made of a material which has a higher selectivity ratio with respect to reactive ion etching than the non-magnetic material, on the non-magnetic film formed in the non-magnetic film forming step; a patterning step of patterning the high-selectivity film formed in the high-selectivity film forming step, into a predetermined shape; and an etching step of etching the non-magnetic film by reactive ion etching, using the high selectivity film patterned into the predetermined shape as a mask.
In the method according to the present invention as described above, the non-magnetic film is etched by reactive ion etching with the patterned high selectivity film used as a mask. Therefore, the non-magnetic film which forms a magnetic gap can be formed with ease. Also, in the method of manufacturing a magnetic head, a fine magnetic gap can be formed with excellent accuracy since a high selectivity film made of a material having a higher selectivity ratio with respect to reactive etching than the non-magnetic film is used as a mask.
Also, according to the present invention, there is provided an etching method comprising: a high selectivity film forming step of forming, on a material to be etched, a high selectivity film made of a metal material which is more hardly etched through reactive ion etching than the material to be etched; a patterning step of patterning the high selectivity film formed in the high selectivity film forming step, into a predetermined shape; a novolak-resin-based resist forming step of forming a resist made of a novolak-resin-based material, on the high selectivity film patterned into the predetermined shape in the patterning step; and an etching step of etching the material to be etched, by reactive ion etching, using the high selectivity film patterned into the predetermined shape in the patterning step as a mask.